Foamed cement slurries, additives and methods

ABSTRACT

The present invention relates to foamed cement slurries, additives and methods. A foamed cement slurry of the invention comprises a hydraulic cement, sufficient water to form a slurry, sufficient gas to form a foam and an environmentally benign foaming and stabilizing additive comprising a mixture of an ammonium salt of an alkyl ether sulfate surfactant, a cocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamine oxide surfactant, sodium chloride and water.

BACKGROUND OF THE INVENTION 1. Fiend of the Invention

The present invention relates to foamed cement slurries and additives aswell as methods of cementing utilizing the foamed cement slurries andadditives.

2. Description of the Prior Art

Foamed hydraulic cement slurries are commonly utilized in formingstructures above and below ground. In forming the structures, the foamedhydraulic cement composition is pumped into a form or other location tobe cemented and allowed to set therein. Heretofore, foamed cementslurries have included foaming and stabilizing additives which includecomponents such as isopropyl alcohol that interfere with aquatic life.In addition, one or more of the components are often flammable and makethe shipment of the foaming and stabilizing additives expensive. Thus,there is a need for foamed hydraulic cement slurries which includeenvironmentally benign foaming and stabilizing additives that do notinclude flammable components.

In the construction and repair of wells such as oil and gas wells,foamed hydraulic cement slurries are often pumped into locations in thewells to be cemented and allowed to set therein. In primary wellcementing, foamed cement slurries are extensively used to cementoff-shore deep water wells wherein they encounter temperatures varyingbetween 40° F.-50° F. The foamed cement slurries are pumped into theannular spaces between the walls of the well bores and the exteriorsurfaces of pipe strings disposed therein. The foamed cement slurriesare compressible which prevents the inflow of undesirable fluids intothe annular spaces and the foamed cement slurries set therein wherebyannular sheaths of hardened cement are formed therein. The annularcement sheaths physically support and position the pipe strings in thewell bores and bond the exterior surfaces of the pipe strings to thewalls of the well bores whereby the undesirable migration of fluidsbetween zones or formations penetrated by the well bores is prevented.

SUMMARY OF THE INVENTION

The present invention provides foamed cement slurries, additives andmethods of cementing which meet the needs described above and overcomethe deficiencies of the prior art.

A foamed cement slurry of the present invention comprises a hydrauliccement, sufficient water to form a slurry, sufficient gas to form a foamand a foaming and stabilizing additive comprising a mixture of anammonium salt of an alkyl ether sulfate surfactant, a cocoamidopropylbetaine surfactant, a cocoamidopropyl dimethylamine oxide surfactant,sodium chloride and water.

An additive for foaming and stabilizing a cement slurry of thisinvention comprises a mixture of an ammonium salt of an alkyl ethersulfate surfactant, a cocoamidopropyl betaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride andwater.

A method of cementing of this invention comprises the steps of providingor preparing a foamed cement slurry comprising a hydraulic cement,sufficient water to form a slurry, sufficient gas to form a foam, and afoaming and stabilizing additive comprising a mixture of an ammoniumsalt of an alkyl ether sulfate surfactant, a cocoamidopropyl betainesurfactant, a cocoamidopropyl dimethylamine oxide surfactant, sodiumchloride and water; placing the foamed cement slurry in a location to becemented; and allowing the cement slurry to set.

A method of cementing a subterranean zone penetrated by a well bore ofthis invention comprises providing or preparing a foamed cement slurrycomprising a hydraulic cement, sufficient water to form a slurry,sufficient gas to form a foam and a foaming and stabilizing additivecomprising a mixture of an ammonium salt of an alkyl ether sulfatesurfactant, a cocoamidopropyl betaine surfactant, a cocoamidopropyldimethylamine oxide surfactant, sodium chloride and water; placing thefoamed cement slurry in the subterranean zone to be cemented by way ofthe well bore; and allowing the foamed cement slurry to set into a hardimpermeable mass.

The objects, features and advantages of the present invention will bereadily apparent to those skilled in the art upon a reading of thedescription of preferred embodiments which follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention provide improved foamed cementslurries, environmentally benign additives for foaming and stabilizingcement slurries, methods of cementing with foamed cement slurries andplacing the foamed cement slurries in locations to be cemented andmethods of cementing with foamed cement slurries and placing the foamedcement slurries in subterranean zones penetrated by well bores.

A foamed cement slurry of this invention comprises a hydraulic cement;sufficient water to form a slurry; sufficient gas to form a foam; and anenvironmentally benign foaming and stabilizing additive comprising amixture of an ammonium salt of an alkyl ether sulfate surfactant, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride and water.

A variety of hydraulic cements can be utilized in accordance with thepresent invention including, but not limited to, Portland cements, slagcements, silica cements, pozzolana cements and aluminous cements. Ofthese, Portland cements are generally preferred. Portland cements of thetypes defined and described in API Specification For Materials andTesting for Well Cements, API Specification 10B, 22^(nd) Edition, DatedDec. 1, 1997 of the American Petroleum Institute are particularlysuitable. Preferred API Portland cements include Classes A, B, C, G andH with API Classes G and H being more preferred and Class H being themost preferred.

The water in the foamed cement slurry can be fresh water, unsaturatedsalt solutions or saturated salt solutions. Generally, the water in thefoamed cement slurry is present in an amount in the range of from about35% to about 70% by weight of the hydraulic cement therein.

The gas utilized to foam the cement slurry can be air or nitrogen withnitrogen being preferred. Generally, the gas is present in the foamedcement slurry in an amount in the range of from about 10% to about 80%by volume of the slurry.

The ammonium salt of an alkyl ether sulfate surfactant in theenvironmentally benign foaming and stabilizing additive is a mixture of29.36% by weight of an ammonium salt of a C₆₋₁₀ alkyl ether sulfatecontaining 1.8 moles of ethylene oxide, 9.79% by weight of an ammoniumsalt of a C₄ alkyl ether sulfate containing 2 moles of ethylene oxide,and 0.40% by weight of ammonium sulfate. The ammonium salt of an alkylether sulfate surfactant is present in the foaming and stabilizingadditive in an amount of about 39.55% by weight of the additive.

The cocoamidopropyl betaine surfactant in the environmentally benignfoaming and stabilizing additive is present in the additive in an amountof about 9.46% by weight of the additive. The cocoamidopropyldimethylamine oxide surfactant in the foaming and stabilizing additiveis present therein in an amount of about 1.39% by weight of theadditive. The sodium chloride in the foaming and stabilizing additive ispresent therein in an amount of about 8.89% by weight of the additiveand the water in the foaming and stabilizing additive is present thereinin an amount of about 40.71% by weight of the additive.

The environmentally benign foaming and stabilizing additive of thisinvention is present in the foamed cement slurry in an amount in therange of from about 0.08% to about 10% by volume of the water in thefoamed cement slurry.

A foamed cement slurry of this invention comprises: a hydraulic cement;sufficient water to form a slurry; sufficient gas to form a foam; and anenvironmentally benign foaming and stabilizing additive comprising amixture of an ammonium salt of an alkyl ether sulfate surfactant, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride and water. The amounts of thecomponents in the foamed cement slurry are the same as those set forthabove and the amounts of the components of the environmentally benignfoaming and stabilizing additive are the same as those set forth above.

An environmentally benign additive of this invention for foaming andstabilizing a cement slurry comprises a mixture of an ammonium salt ofan alkyl ether sulfate surfactant, a cocoamidopropyl betaine surfactant,a cocoamidopropyl dimethylamine oxide surfactant, sodium chloride andwater. The amounts of the components in the additive are the same asthose set forth above.

A method of cementing of the present invention comprises the steps of:preparing a foamed cement slurry comprising a hydraulic cement,sufficient water to form a slurry, sufficient gas to form a foam, and anenvironmentally benign foaming and stabilizing additive comprising amixture of an ammonium salt of an alkyl ether sulfate surfactant, acocoamidopropyl betaine surfactant, a cocoamidopropyl dimethylamineoxide surfactant, sodium chloride and water; placing the foamed cementslurry in a location to be cemented; and allowing the cement slurry toset. The amounts of the components in the foamed cement slurry are thesame as those set forth above and the amounts of the components of theenvironmentally benign foaming and stabilizing additive are the same asthose set forth above.

Finally, a method of cementing a subterranean zone penetrated by a wellbore of this invention comprises the steps of: preparing a foamed cementslurry comprising a hydraulic cement, sufficient water to form a slurry,sufficient gas to form a foam, and an environmentally benign foaming andstabilizing additive comprising a mixture of an ammonium salt of analkyl ether sulfate surfactant, a cocoamidopropyl betaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride andwater; placing the foamed cement slurry in the subterranean zone by wayof the well bore; and allowing the foamed cement slurry to set into ahard impermeable mass. The amounts of the components in the foamedcement slurry are the same as those set forth above and the amounts ofthe components in the environmentally benign foaming and stabilizingadditive are the same as set forth above.

In order to further illustrate the cement slurries, the environmentallybenign additives for foaming and stabilizing a cement slurry, themethods of cementing in a location to be cemented, and the methods ofcementing a subterranean zone penetrated by a well bore, the followingexamples are given.

EXAMPLE 1

An environmentally benign additive for foaming and stabilizing a cementslurry of this invention was prepared in the laboratory consisting of anammonium salt of an alkyl ether sulfate surfactant (90% active) presentin the mixture in an amount of 39.55% by weight of the mixture, acocoamidopropyl betaine surfactant (30% active) present in an amount of31.52% by weight of the mixture, a cocoamidopropyl dimethylamine oxidesurfactant (30% active) present in an amount of 4.63% by weight of themixture, sodium chloride present in an amount of 7.31% by weight of themixture, and water present in the mixture in an amount of 16.99% byweight of the mixture.

The ammonium salt of an alkyl ether sulfate surfactant consisted of amixture of an ammonium salt of a C₆₋₁₀ alkyl ether sulfate surfactantcontaining 1.8 moles of ethylene oxide present in an amount of 29.36% byweight, an ammonium salt of a C₄ alkyl ether sulfate surfactantcontaining 2 moles of ethylene oxide present in an amount of 9.79% byweight, and 0.4% by weight of ammonium sulfate.

The foaming properties, foam stability and uniformity of the foamedcement after setting was determined for a foamed cement slurrycomprising Portland Class H cement and water prepared in a multi-bladefoam generator having a density of 16.49 pounds per gallon. To a portionof the foamed cement slurry, the environmentally benign foaming andstabilizing additive of this invention was added in an amount of 2% byweight. To a second portion of the foamed cement slurry, a prior artfoaming and stabilizing additive was added in an amount of 2% by weight.The prior art foaming and stabilizing additive comprises a mixture ofethoxylated alcohol ether sulfate, an alkyl or alkene amidopropylbetaine and an alkyl or alkene amidopropyl dimethylamine oxide. Thissurfactant is described and claimed in U.S. Pat. No. 6,063,738 issued onMay 16, 2000 to Chatterji et al. entitled FOAMED WELL CEMENT SLURRIES,ADDITIVES AND METHODS which is incorporated herein by reference thereto.

The foaming and stabilizing additives were added to the cementcompositions in amounts of 2% by volume of the water therein. Thecalculated density, 15 second density and 72 hours compressive strengthat 140° F. were determined for each of the cement compositions. Also,the densities of the compositions after setting were determined at thetop, middle and bottom of the set compositions. The results of thesetests are set forth in TABLE I below. TABLE I Portland Class H Cementand Water (Base Density - 16.49 lb/gal) Foaming and Stabilizing 72 HourAdditive 15 Com- and % Calculated Second pressive By Volume DensityDensity Strength Density After Set (lb/gal) of Water (lb/gal) (lb/gal)(psi) Top Middle Bottom 2% 11 10.22 1070 10.58 9.95 9.8 Prior ArtAdditive 2% 11 10.26 969 10.18 9.77 9.77 Present Invention Additive

From Table I, it can be seen that the environmentally benign foaming andstabilizing additive of the present invention functions substantially aswell as the prior art foaming and stabilizing additive which is notenvironmentally benign.

EXAMPLE 2

The tests described above and set forth in Table I were repeated using acement composition containing salt, i.e., a cement compositioncomprising Joppa Class H cement, 15% amorphous silica by weight ofcement, 37% sodium chloride by weight of cement and water having adensity of 15.62 pounds per gallon. The results of the tests are givenin Table II below. TABLE II Joppa Class H Cement, 15% Amorphous Silica,37% Sodium Chloride and Water (Base Density - 15.62 lb/gal) Foaming andStabilizing 72 Hour Additive 15 Com- and % Calculated Second pressive ByVolume Density Density Strength Density After Set (lb/gal) of Water(lb/gal) (lb/gal) (psi) Top Middle Bottom 2% 11.2 11.76 1038 11.02 11.1111.20 Prior Art Additive 2% 11.2 11.01 876 10.57 10.70 10.71 PresentInvention Additive

From Table II, it can be seen that the environmentally benign foamingand stabilizing additive of this invention functioned well in thepresence of salt.

EXAMPLE 3

The tests described in Example 1 above were repeated utilizing a cementcomposition formed with sea water, i.e., a cement composition comprisingJoppa Class H cement and sea water having a base density of 16.62 poundsper gallon. The results of the tests are set forth in Table III below.TABLE III Joppa Class H and Sea Water (Base Density - 16.62 lb/gal)Foaming and Stabilizing 72 Hour Additive 15 Com- and % Calculated Secondpressive By Volume Density Density Strength Density After Set (lb/gal)of Water (lb/gal) (lb/gal) (psi) Top Middle Bottom 2% 11 10.20 1036 9.769.78 9.78 Prior Art Additive 2% 11 10.23 927 10.94 10.27 9.86 PresentInvention Additive

From Table III, it can be seen that the environmentally benign foamingand stabilizing additive of the present invention functioned as well orbetter in sea water than the prior art foaming and stabilizing additive.

EXAMPLE 4

The tests described in Example 1 above were repeated utilizing a cementcomposition containing slag, i.e., a cement composition containing slag,sodium carbonate in an amount of 8% by weight of the slag and water. Theresults of the tests are set forth in Table IV below. TABLE IV Slag, 8%Sodium Carbonate and Water (Base Density - 15.0 lb/gal) Foaming andStabilizing 72 Hour Additive 15 Com- and % Calculated Second pressive ByVolume Density Density Strength Density After Set (lb/gal) of Water(lb/gal) (lb/gal) (psi) Top Middle Bottom 2% 11 12.02 2070 12.15 12.112.14 Prior Art Additive 2% 11 11.27 2175 11.44 11.52 11.55 PresentInvention Additive

From Table IV, it can be seen that the environmentally benign foamingand stabilizing additive of the present invention functions as well asthe prior art foaming and stabilizing additive.

EXAMPLE 5

The tests described in Example 1 were repeated utilizing a cementcomposition comprising Class F fly ash, hydrated lime in an amount of15% by weight of the fly ash, calcium chloride present in an amount of4% by weight of the fly ash and water. The results of the tests are setforth in Table V below. TABLE V Class F Fly Ash, 15% Hydrated Lime, 4%Calcium Chloride and Water (Base Density - 14.08 lb/gal) Foaming andStabilizing 72 Hour Additive 15 Com- and % Calculated Second pressive ByVolume Density Density Strength Density After Set (lb/gal) of Water(lb/gal) (lb/gal) (psi) Top Middle Bottom 2% 10 9.57 692 9.28 9.19 9.18Prior Art Additive 2% 10 9.40 681 9.17 8.88 8.87 Present InventionAdditive

From Table V, it can again be seen that the environmentally benignfoaming and stabilizing additive functioned as well as the prior artadditive in a fly ash cement composition.

EXAMPLE 6

The tests set forth in Example 1 were repeated utilizing a cementcomposition comprising micro matrix cement and water. The results of thetests are set forth in Table VI below. TABLE VI Matrix Cement and Water(Base Density - 12.5 lb/gal) Foaming and Stabilizing 72 Hour Additive 15Com- and % Calculated Second pressive By Volume Density Density StrengthDensity After Set (lb/gal) of Water (lb/gal) (lb/gal) (psi) Top MiddleBottom 2% 10 9.46 974 9.46 9.53 9.5 Prior Art Additive 2% 10 9.62 10349.52 9.6 9.59 Present Invention Additive

From Table VI, it can again be seen that the environmentally benignfoaming and stabilizing additive of this invention functioned as well orbetter than the prior art foaming and stabilizing additive.

EXAMPLE 7

The tests set forth in Example 1 were repeated utilizing a cementcomposition comprising calcium aluminate, ASTM Class F fly ash and wateras described in U.S. Pat. No. 6,332,921 issued on Dec. 25, 2001 toBrothers et al., which is incorporated herein by reference thereto. Theresults of the tests are set forth in Table VII below. TABLE VII CalciumAluminate, ASTM Class F Fly Ash and Water (Base Density - 15.02 lb/gal)Foaming and Stabilizing 72 Hour Additive 15 Com- and % Calculated Secondpressive By Volume Density Density Strength Density After Set (lb/gal)of Water (lb/gal) (lb/gal) (psi) Top Middle Bottom 2% 11 9.46 974 9.469.53 9.5 Prior Art Additive 2% 11 9.62 1034 9.52 9.6 9.59 PresentInvention Additive

From Table VII it can be seen that the environmentally benign foamingand stabilizing additive of this invention functioned as well as orbetter than the prior art foaming and stabilizing additive.

EXAMPLE 8

In order to determine the ability of the environmentally benign foamingand stabilizing additive of the present invention to foam at lowtemperatures, the following experiment was performed. A Joppa Class Hcement slurry containing 2% of the environmentally benign foaming andstabilizing additive in an amount of 2% by weight of the water in thecement slurry having a density of 16.49 pounds per gallon was foamed atambient temperature and pressure to a density of 10.24 pounds per gallon(the desired density was 11.0 pounds per gallon). The foamed slurry wasstirred in an atmospheric consistometer for one hour at 50° F. At theend of the stirring, the foamed slurry had a density of 9.96 pounds pergallon. The slurry was then cured at 55° F. for 72 hours. The experimentwas repeated utilizing the prior art foaming and stabilizing additive.The results of the tests are set forth in Table VIII below. TABLE VIIIJoppa Class H Cement and Water (Base Density - 16.49 lb/gal) Foaming andStabilizing Additive Cal- 15 and % culated Second Density @ 1 By VolumeDensity Density Hour Density After Set (lb/gal) of Water (lb/gal)(lb/gal) (lb/gal) Top Middle Bottom 2% 11 10.21 14.33 15.42 16.49 17.47Prior Art Additive 2% 11 10.24 9.96 10.24 10.32 10.84 Present InventionAdditive

From Table VIII, it can be seen that the environmentally benign foamingand stabilizing additive cured sufficiently at 55° F.

EXAMPLE 9

Foam transfer data using a MACS analyzer was determined for a 16 poundper gallon slurry consisting of Joppa Class H cement, crystalline silicapresent in an amount of 35% by weight of the cement, amorphous silicapresent in an amount of 5% by weight of cement, a non-dispersing setretarder present in an amount of 0.6% by weight of the cement and theenvironmentally benign foaming and stabilizing additive of the presentinvention present in an amount of 2% by volume of water in the cementslurry. The non-dispersing retarder utilized is described in U.S. Pat.No. 6,227,294 issued to Chatterji et al. on May 8, 2001 which isincorporated herein by reference thereto.

The cement composition described above was foamed at 200° F. and apressure of 1000 psi in the MACS analyzer, i.e., an instrument known asa multiple analysis cement slurry (MACS) analyzer. The foamed cementslurry in the MACS analyzer was transferred at 200° F. through amanifold system to curing cells that were preheated and charged withnitrogen at the same pressure to which the slurry is subjected in themixing chamber of the analyzer. The foamed slurry had density of 10.91pounds per gallon (desired density was 11.5 pounds per gallon). Thefoamed cement composition was cured at a temperature of 250° F. for aperiod of 72 hours. Thereafter the densities of the top, middle andbottom of the cured sample was measured.

The results of these tests are set forth in Table IX below. TABLE IXJoppa Class H Cement, Crystalline Silica, Amorphous Silica, Set Retarderand Water (Base Density - 16.0 lb/gal) Foaming and Stabilizing TransferAdditive and % Calculated Cell By Volume Density Density Density AfterSet (lb/gal) of Water (lb/gal) (lb/gal) Top Middle Bottom 2% 11.5 9.6210.66 11.09 11.32 Present Invention Additive

From Table IX, it can be seen that the sample cured under hightemperature and pressure has a minimum variation of density from top tobottom.

Thus, the present invention is well adapted to carry out the objects andattain the ends and advantages mentioned as well as those inherenttherein. While numerous changes may be made by those skilled in the art,such changes are encompassed within the spirit of this invention asdefined by the appended claims.

1-18. (canceled)
 19. A method of cementing comprising the steps of:providing a foamed cement slurry comprising a hydraulic cement, water, agas, and a foaming and stabilizing additive comprising a mixture of anammonium salt of an alkyl ether sulfate surfactant, cocoamidopropylbetaine surfactant, cocoamidopropyl dimethylamine oxide surfactant,sodium chloride and water, wherein the ammonium salt of the alkyl ethersulfate surfactant comprises a mixture of an ammonium salt of a C₆₋₁₀alkyl ether sulfate surfactant, an ammonium salt of a C₄ alkyl ethersulfate surfactant and an ammonium sulfate; placing the foamed cementslurry in a location to be cemented; and allowing the cement slurry toset.
 20. The method of claim 19 wherein the hydraulic cement comprisesat least one of the following: a Portland cement, a slag cement, asilica cement, a pozzolana cement or an aluminous cement.
 21. The methodof claim 19 wherein the water comprises at least one of the following:fresh water, an unsaturated salt solution or a saturated salt solution.22. The method of claim 19 wherein the water in the foamed cement slurryis present in an amount in the range of from about 35% to about 70% byweight of hydraulic cement therein.
 23. The method of claim 19 whereinthe gas comprises at least one of the following: air or nitrogen. 24.The method of claim 19 wherein the gas in the foamed cement slurry ispresent in the range of from about 10% to about 80% by volume of thecement slurry.
 25. The method of claim 19 wherein the mixture thatcomprises the ammonium salt of the alkyl ether sulfate surfactantcomprises 29.36% by weight of the ammonium salt of the C₆₋₁₀ alkyl ethersulfate surfactant containing 1.8 moles of ethylene oxide, 9.79% byweight of the ammonium salt of the C₄ alkyl ether sulfate surfactantcontaining 2 moles of ethylene oxide, and 0.40% by weight of theammonium sulfate.
 26. The method of claim 19 wherein the cocoamidopropylbetaine surfactant in the foaming and stabilizing additive is present inan amount of about 9.46% by weight of the additive.
 27. The method ofclaim 19 wherein the cocoamidopropyl dimethylamine oxide surfactant inthe foaming and stabilizing additive is present in an amount of about1.39% by weight of the additive.
 28. The method of claim 19 wherein thesodium chloride in the foaming and stabilizing additive is present in anamount of about 8.89% by weight of the additive.
 29. The method of claim19 wherein the water in the foaming and stabilizing additive is presentin an amount of about 40.71% by weight of the additive.
 30. The methodof claim 19 wherein the foaming and stabilizing additive in the foamedcement slurry is present in an amount in the range of from about 0.8% toabout 10% by volume of the water in the foamed cement slurry.
 31. Themethod of claim 19 wherein the location to be cemented is above ground,below ground or in a well.
 32. A method of cementing a subterranean zonepenetrated by a well bore comprising the steps of: providing a foamedcement slurry comprising a hydraulic cement, water, a gas, and a foamingand stabilizing additive comprising a mixture of an ammonium salt of analkyl ether sulfate surfactant, cocoamidopropyl betaine surfactant,cocoamidopropyl dimethylamine oxide surfactant, sodium chloride andwater, wherein the ammonium salt of the alkyl ether sulfate surfactantcomprises a mixture of an ammonium salt of a C₆₋₁₀ alkyl ether sulfatesurfactant, an ammonium salt of a C₄ alkyl ether sulfate surfactant, andan ammonium sulfate; placing the foamed cement slurry in thesubterranean zone by way of the well bore; and allowing the foamedcement slurry to set into a hard impermeable mass.
 33. The method ofclaim 32 wherein the hydraulic cement comprises at least one of thefollowing: a Portland cement, a slag cement, a silica cement, apozzolana cement or an aluminous cement.
 34. The method of claim 32wherein the water comprises at least one of the following: fresh water,an unsaturated salt solution or a saturated salt solution.
 35. Themethod of claim 32 wherein the water in the foamed cement slurry ispresent in an amount in the range of from about 35% to about 70% byweight of hydraulic cement therein.
 36. The method of claim 32 whereinthe gas comprises at least one of the following: air or nitrogen. 37.The method of claim 32 wherein the gas in the foamed cement slurry ispresent in the range of from about 10% to about 80% by volume of thecement slurry.
 38. The method of claim 32 wherein the mixture thatcomprises the ammonium salt of the alkyl ether sulfate comprises 29.36%by weight of the ammonium salt of the C₆₋₁₀ alkyl ether sulfatesurfactant containing 1.8 moles of ethylene oxide, 9.79% by weight of anammonium salt of a C₄ alkyl ether sulfate surfactant containing 2 molesof ethylene oxide, and 0.40% by weight of the ammonium sulfate.
 39. Themethod of claim 32 wherein the cocoamidopropyl betaine surfactant in thefoaming and stabilizing additive is present in an amount of about 9.46%by weight of the additive.
 40. The method of claim 32 wherein thecocoamidopropyl dimethylamine oxide surfactant in the foaming andstabilizing additive is present in an amount of about 1.39% by weight ofthe additive.
 41. The method of claim 32 wherein the sodium chloride inthe foaming and stabilizing additive is present in an amount of about8.89% by weight of the additive.
 42. The method of claim 32 wherein thewater in the foaming and stabilizing additive is present in an amount ofabout 40.71% by weight of the additive.
 43. The method of claim 32wherein the foaming and stabilizing additive in the foamed cement slurryis present in an amount in the range of from about 0.8% to about 10% byvolume of the water in the foamed cement slurry.